[Docs] add markdown docs (converted from Wiki)

BUG=none
R=mark
CC=google-breakpad-dev@googlegroups.com

Review URL: https://codereview.chromium.org/1357773004 .

Patch from Andy Bonventre <andybons@chromium.org>.

docs/contributing_to_breakpad.md

@@ -0,0 +1,35 @@
+# Introduction
+
+Thanks for thinking of contributing to Breakpad! Unfortunately there are some
+pesky legal issues to get out of the way, but they're quick and painless.
+
+## Legal
+
+If you're doing work individually, not as part of any employment, you'll need to
+sign the <a
+href='http://code.google.com/legal/individual-cla-v1.0.html'>Individual
+Contributor License Agreement</a>. This agreement can be completed
+electronically.
+
+If you're contributing to Breakpad as part of your employment with another
+organization, you'll need to sign a <a
+href='http://code.google.com/legal/corporate-cla-v1.0.html'> Corporate
+Contributor License Agreement</a>. Once completed this document will need to be
+faxed.
+
+**_IMPORTANT_**: The authors(you!) of the contributions will maintain all
+copyrights; the agreements you sign will grant rights to Google to use your
+work.
+
+Thanks, and if you have any questions let me know and I'll loop in the legal guy
+here to get you an answer.
+
+## Technical
+
+Once you have signed the agreement you can be added to our contributors list and
+have write access to code. For full details on getting started see our trunk
+`README`.
+
+## List of people who have signed contributor agreements
+
+None so far.